The present invention relates to computer communication network repeaters, and more specifically, the present invention relates to sharing resources of a repeater and a plurality of Medium Attachment Units integrated into a single integrated circuit device.
Prior art repeaters typically comprise multiple discrete devices for implementing an IEEE 802.3 Standard, this standard incorporated by reference for all purposes. The IEEE 802.3 Standard specifies a relay function and a port function. The repeater's purpose is to extend a local area network and to allow multiple nodes physically separated from each other to communicate with each other. The relay function receives a data packet from a first node at a first port with the data packet destined for another node at another port. Prior art repeaters may have almost any number of ports. The relay function retimes the data packet and restores proper amplitude to the received data packet. The repeater then retransmits the data packet to all its ports, and the proper node is able to respond. Prior art repeaters include a number of discrete ports which receive and transmit data as appropriate. The port function is different from the relay function.
Construction of the network may use different media types for transmission of a signal. These media include, for example, coaxial cable, shielded twisted pair cable and fiber optic cable. The different media types require different signal parameters to optimize performance of the network when using any particular medium. The network may also include a combination of medium types. The IEEE 802.3 Standard specifies general signalling characteristics and signal requirements for using these media. The general signal characteristics provide a convention for each node or repeater in presenting or receiving a signal to the network medium. A device referred to as a Medium Attachment Unit (MAU) translates the general signal information from a node or repeater to a medium specific signal. The MAU also translates the medium specific signal into the general signal. Thus, a repeater must have a MAU associated with each port. The MAU function is different than either the port function or the relay function.
A standard, IEEE 802.3 10BASE-T defines this translation function for a twisted pair medium, the standard hereby incorporated by reference for all purposes. Networks using twisted pair wiring have a star configuration, with a repeater as a hub of a star. Linking segments may interconnect a port of one repeater with another repeater port. A single node connects to the other ports of the repeater. Due to signal delays, there is a limit to a maximum number of repeaters through which a signal from a node may pass before receipt at a second node. This limit is four repeaters.
The MAU performs a number of functions that include implementation of a link integrity test (linktest) by generating idle linktest pulses (linkbeats). The IEEE 802.3 Standard also defines a Link Integrity Status feature incorporated into the MAUs. Each MAU must separately satisfy the requirements of the IEEE 802.3 Standard. The linkbeat requirements specify that a linkbeat must be received in a maximum predetermined interval, whose value may range between 50 ms and 150 ms. Additionally, the standard requires a minimum time interval between received linkbeats to elapse. Conventional systems use two timers to establish the necessary intervals to determine if a failure occurred and a third timer for generation of linkbeats. Each port requires three timers. Each MAU uses its own timers because each MAU's linkbeats are asynchronous relative to other linkbeats at the other MAUs.
MAUs constructed prior to the IEEE 802.3 Standard have not always provided for linkbeat generation. Some networks may use MAUs which do not generate linkbeats. Maintaining backward compatibility for newer MAUs (repeaters), added to such networks, is crucial. Thus, newer repeater units should not necessarily fail an older node (i.e. deactivate transmission and receive activity relative to the particular port coupled to the node) which does not generate linkbeats.
Another function a repeater performs is extracting data from an input signal. Extracting data from the data packets transmitted over the network by a repeater unit is necessary as the repeater unit retimes the data and provides the correct amplitude. The data packet encoding uses Manchester format which is a Boolean EXCLUSIVE OR combination of the data and the clock. To extract the data, a phase-locked loop first extracts the clock. A second EXCLUSIVE OR combination of the extracted clock and the Manchester formatted data extracts the data. This function is required for each of the ports in a repeater unit.
What is desirable is an integrated device combining the relay function with MAU and port functions simplifying construction of a repeater and reducing its costs. The integrated multi-port repeater (IMR) needs to include a number of ports, each with a MAU and perhaps an attachment unit interface (AUI). For an IMR having eight ports, for example, implementing the linkbeat and the data extraction requires 24 linkbeat timers and 8 phase-locked loop circuits. Reduction of this hardware is a desirable feature of the present invention. Additionally, maintaining backward linkbeat compatibility for repeater units added to networks existing before the linkbeat requirement is another feature of the present invention.
Repeater/hub management operations typically require that some external management system monitor activity of each repeater port to provide statistical information. This information may be used for accounting purposes, for example. An important signal in these management operations is the carrier sense signal. Assertion of carrier sense by a port indicates that the port is sensing activity on the network. Each MAU has an independent carrier sense signal. Integration of the MAUs into the IMR provides a situation in which access to the carrier sense signals of each of the MAUs by an external management system is difficult. A straightforward solution adds a pin for each carrier sense signal but this adds one pin per port per IMR chip. Integrated circuit pin limitations constrain this solution as chip cost is directly related to the number of pins. Therefore, it is a feature of the present invention to provide a streamlined mechanism to monitor port activity.